Interacting Floquet polaritons.

Ordinarily, photons do not interact with one another. However, atoms can be used to mediate photonic interactions1,2, raising the prospect of forming synthetic materials3 and quantum information systems4-7 from photons. One promising approach combines highly excited Rydberg atoms8-12 with the enhanced light-matter coupling of an optical cavity to convert photons into strongly interacting polaritons13-15. However, quantum materials made of optical photons have not yet been realized, because the experimental challenge of coupling a suitable atomic sample with a degenerate cavity has constrained cavity polaritons to a single spatial mode that is resonant with an atomic transition. Here we use Floquet engineering16,17-the periodic modulation of a quantum system-to enable strongly interacting polaritons to access multiple spatial modes of an optical cavity. First, we show that periodically modulating an excited state of rubidium splits its spectral weight to generate new lines-beyond those that are ordinarily characteristic of the atom-separated by multiples of the modulation frequency. Second, we use this capability to simultaneously generate spectral lines that are resonant with two chosen spatial modes of a non-degenerate optical cavity, enabling what we name 'Floquet polaritons' to exist in both modes. Because both spectral lines correspond to the same Floquet-engineered atomic state, adding a single-frequency field is sufficient to couple both modes to a Rydberg excitation. We demonstrate that the resulting polaritons interact strongly in both cavity modes simultaneously. The production of Floquet polaritons provides a promising new route to the realization of ordered states of strongly correlated photons, including crystals and topological fluids, as well as quantum information technologies such as multimode photon-by-photon switching.

Current role of Nuclear Medicine in the diagnosis and therapy of gastroenteropancreatic neuroendocrine tumors (GEP-NETs).

Neuroendocrine tumors (NETs), are heterogenic neoplasms that arise from the disseminated endocrine cell system, primarily from gastroenteropancreatic (GEP) organs. Nuclear Medicine has a central role in both diagnosis and treatment of GEP-NETs. Somatostatin receptor scintigraphy (SRS) is still performed with SPECT/CT in case that PET/CT is not available but numerous studies have demonstrated the superior diagnostic accuracy of the latter for GEP-NETs. 68Ga -Dota peptide PET/CT (SSA-PET/CT) has high sensitivity, specificity and accuracy (86%-100%) and is recommended for the staging as also for the restaging of GEP-NETs.

Visceral adipose tissue phenotype and hypoadiponectinemia are associated with aortic Fluorine-18 fluorodeoxyglucose uptake in patients with familial dyslipidemias.

BACKGROUND: The role of adipose tissue (AT) in arterial inflammation in familial dyslipidaemias is poorly studied. We investigated the relationship between AT and arterial inflammation in patients with heterozygous familial hypercholesterolemia (heFH) and familial combined hyperlipidemia (FCH). METHODS AND RESULTS: A total of 40 patients (20 heFH/20 FCH) and a subgroup of 20 of non-heFH/FCH patients were enrolled. Participants underwent blood sampling for serum adipokine measurements and Fluorine-18 fluorodeoxyglucose (18F-FDG) PET/CT imaging. Abdominal visceral (VAT) and subcutaneous (SAT) AT volumes and AT and abdominal aorta 18F-FDG uptake were quantified. FCH patients had increased VAT (pANOVA = 0.004) and SAT volumes (pANOVA = 0.003), lower VAT metabolic activity (pANOVA = 0.0047), and lower adiponectin levels (pANOVA = 0.007) compared to heFH or the control group. Log(Serum adiponectin) levels were correlated with aortic TBR (b = - 0.118, P = 0.038). In mediation analysis, VAT volume was the major determinant of circulating adiponectin, an effect partly mediated via VAT TBR. Clustering of the population of heFH/FCH by VAT volume/TBR and serum adiponectin identified two distinct patient clusters with significant differences in aortic TBR levels (2.11 ± 0.06 vs 1.89 ± 0.05, P= 0.012). CONCLUSIONS: VAT phenotype (increased VAT volume and/or high VAT TBR) and hypoadiponectinemia may account for the observed differences in arterial inflammation levels between heFH and FCH patients.

Fluorine-18 fluorodeoxyglucose positron emission tomography-based textural features for prediction of event prone carotid atherosclerotic plaques.

BACKGROUND: Texture analysis has been increasingly used in the field of positron emission tomography (PET)/computed tomography (CT) imaging with Fluorine-18 fluorodeoxyglucose (18F-FDG), aiming at assessing tumor heterogeneity. The purpose of the present study is to examine the feasibility of performing texture analysis in carotid arteries, investigate the value of textural features as predictors of potential plaque vulnerability using as reference standards histological and immunohistochemical data and compare their performance with conventional uptake measurements. METHODS: 67 different 18F-FDG PET-based textural features were extracted from carotid images of 21 patients with high-grade carotid stenosis undergoing endarterectomy. To identify the more reliable predictors, univariate logistic regression analysis was performed. The accuracy was satisfactory in case of an Area Under the Receiver Operating Characteristic (ROC) curve (AUC) ≥ 0.80. RESULTS: First measure of information correlation (AUC = 0.87, P < 0.001), large zone low gray level emphasis (AUC = 0.87, P < 0.001), and normalized run length non-uniformity (AUC = 0.84, P < 0.001) were the most optimal textural features for identifying characteristics of plaque vulnerability based on histological analysis. Addition of textural features to target-to-background ratio (TBR) (AUC = 0.74, P = 0.031) resulted in an AUC = 0.92 (P < 0.001), however, this did not reach statistical significance (Pdiff = 0.09). Intensity histogram standard deviation (AUC = 0.87, P < 0.001) and joint variance (AUC = 0.81, P = 0.001) were the most efficient features for signal differential in relation to immunohistochemical findings and provided incremental value compared to TBR (Pdiff = 0.02). CONCLUSION: Texture analysis can be applied in 18F-FDG PET carotid imaging providing valuable information for plaque characterization.

Central nervous system disorders affecting the heart-insights from radionuclide imaging.

There is a growing research activity focusing on the brain heart cross-talk. A great variety of brain disorders affect the heart and recent developments in neurosciences have revealed the particular role of specific neuroanatomic sites on heart rhythm and rate, myocardial function and vascular tone. Cardiac radionuclide imaging plays a pivotal role in this setting, since not only helps elucidating underlying pathobiological mechanisms but in addition, it promises exciting possibilities for early identification of patients at risk of developing cardiovascular manifestations of certain neurological diseases.

From Karl Wurm and Guy Scadding's staging to 18F-FDG PET/CT scan phenotyping and far beyond: perspective in the evading history of phenotyping in sarcoidosis.

Sarcoidosis is an inflammatory granulomatous disease of unknown etiology involving any organ or tissue along with any combination of active sites, even the most silent ones clinically. The unpredictable nature of the sites involved in sarcoidosis dictates the highly variable natural history of the disease and the necessity to cluster cases at diagnosis based on clinical and/or imaging common characteristics in an attempt to classify patients based on their more homogeneous phenotypes, possibly with similar clinical behavior, prognosis, outcome, and therefore with therapeutic requirements. In the course of the disease's history, this attempt relates to the availability of a means of detection of the sites involved, from the Karl Wurm and Guy Scadding's chest x-ray staging through the ACCESS, the WASOG Sarcoidosis Organ Assessment Instruments, and the GenPhenReSa study to the 18F-FDG PET/CT scan phenotyping and far beyond to new technologies and/or the current "omics." The hybrid molecular imaging of the 18F-FDG PET/CT scan, by unveiling the glucose metabolism of inflammatory cells, can identify high sensitivity inflammatory active granulomas, the hallmark of sarcoidosis-even in clinically and physiologically silent sites-and, as recently shown, is successful in identifying an unexpected ordered stratification into four phenotypes: (I) hilar-mediastinal nodal, (II) lungs and hilar-mediastinal nodal, (III) an extended nodal supraclavicular, thoracic, abdominal, inguinal, and (IV) all the above in addition to systemic organs and tissues, which is therefore the ideal phenotyping instrument. During the "omics era," studies could provide significant, distinct, and exclusive insights into sarcoidosis phenotypes linking clinical, laboratory, imaging, and histologic characteristics with molecular signatures. In this context, the personalization of treatment for sarcoidosis patients might have reached its goal.

Tumor Size Measurements for Predicting Hodgkin's and Non-Hodgkin's Lymphoma Response to Treatment.

The purpose of this study was to investigate the value of tumor size measurements as prognostic indicators of treatment outcome of Hodgkin's and Non-Hodgkin's lymphomas. 18F-FDG PET/CT exams before and after treatment were analyzed and metabolic and anatomic parameters-tumor maximum diameter, tumor maximum area, tumor volume, and maximum standardized uptake value (SUVmax)-were determined manually by an expert and automatically by a computer algorithm on PET and CT images. Results showed that the computer algorithm measurements did not correlate well with the expert's standard maximum tumor diameter measurements but yielded better three dimensional metrics that could have clinical value. SUVmax was the strongest prognostic indicator of the clinical outcome after treatment, followed by the automated metabolic tumor volume measurements and the expert's metabolic maximum diameter measurements. Anatomic tumor measurements had poor prognostic value. Metabolic volume measurements, although promising, did not significantly surpass current standard of practice, but automated measurements offered a significant advantage in terms of time and effort and minimized biases and variances in the PET measurements. Overall, considering the limited value of tumor size in predicting response to treatment, a paradigm shift seems necessary in order to identify robust prognostic markers in PET/CT; radiomics, namely combinations of anatomy, metabolism, and imaging, may be an option.

Emerging phenotypes of sarcoidosis based on 18F-FDG PET/CT: a hierarchical cluster analysis.

Objectives: In sarcoidosis, the definition of organ involvement with traditional means appears laborious and somewhat controversial, and phenotyping by the above overlapping. 18F-FDG PET/CT defines disease extent by activity more precisely, and may result in a better understanding of sarcoidosis disease behavior and phenotypes expression. We hypothesized that 18F-FDG PET/CT could add in the phenotyping of sarcoidosis patients by unveiling in detail sites of involvement even in clinically and physiologically silent disease.Methods: This study was designed to investigate the role of 18F-FDG PET/CT in phenotyping sarcoidosis using cluster analysis by adding this new means in the routine work-up of 195 sarcoidosis patients of a single academic center.Results: 18F-FDG PET/CT succeeded to identify despite the random distribution of the disease, an ordered stratification into 4 phenotypes: I) thoracic nodal hilar-mediastinal, II) thoracic nodal hilar-mediastinal and lungs, III) an extended thoracic and extra-thoracic only nodal phenotype including inguinal-abdominal-supraclavicular stations, and IV) all the above plus systemic organs and tissues such as muscles-bones-spleen and skin.Conclusion: Though further studies are necessary to confirm findings as patterns of disease behavior; the proposed phenotypes may prove useful in the design of future studies with homogeneous cohorts facilitating in sarcoidosis patients a personalized medicine approach.

18F-FDG PET/CT in Pulmonary Sarcoidosis:Quantifying Inflammation by the TLG index.

Objectives: In sarcoidosis progressive pulmonary disease affects prognosis. Pulmonary disease activity estimated by classic means poorly predicts severity and progressiveness. 18F-fluoro-2-deoxyglucose-positron-emission-tomography computed-tomography (18F-FDG-PET/CT) estimates pulmonary activity by inflammatory-cells metabolism. We aimed to investigate pulmonary sarcoidosis by 18F-FDG-PET/CT and evaluate the role of total-lesion-glycolysis (TLG) value, as an index quantifying the whole burden of lung inflammation.Methods: This is a retrospective study of sequentially gathered data. From a Greek cohort of 195 sarcoidosis-patients, 87 were identified with lung increased 18F-FDG uptake and further studied.Results: Visualizing lung by 18F-FDG-PET/CT identified new imaging patterns and revealed activity in all Scadding stages. Ever-smokers presented significantly higher TLG and lower DLCO compared to never-smokers. However, TLG value did not correlate with functional indices and did not differ between symptomatic and non-symptomatic patients. Among treatment-naïve patients, TLG did not differ significantly in those requiring therapy compared to those remained off.Conclusion: 18F-FDG PET/CT improved imaging and detection of pulmonary involvement and through TLG value revealed the deleterious smoking effect. The fact that TLG neither detected patients with clinical symptoms and functional impairment nor identified those requiring treatment once again confirms that in pulmonary sarcoidosis the link between activity, severity and decision to treat still eludes us.

Erdheim-Chester Disease and Acute Myeloid Leukemia with Mutated NPM1 in a Patient with Clonal Hematopoiesis: A Case Report.

BACKGROUND: Erdheim-Chester Disease (ECD) is a clonal non-Langerhans histiocytosis, classified as a macrophage-dendritic cell neoplasm in the 2016 WHO classification. The exact cell of origin of ECD is unknown, although some limited evidence suggests that it arises from myeloid progenitors. CASE PRESENTATION: A 43-year-old patient, diagnosed with BRAF V600E mutated ECD, developed NPM1+/FLT3+ acute myeloid leukemia (AML) with wild-type BRAF, 15 months after the initial ECD diagnosis. The patient received intensive chemotherapy plus midostaurin, followed by midostaurin maintenance. Six months into maintenance, the patient remains in complete remission with low-level measurable residual disease, whereas ECD shows a sustained partial metabolic response. Molecular karyotype at several distinct timepoints, namely ECD diagnosis, AML diagnosis, and following treatment of AML, highlighted a molecular signature, indicative of a persistent, underlying clonal hematopoiesis. CONCLUSION: This case report suggests that ECD and AML might represent an expansion of two distinct clones in a background of clonal hematopoiesis, indicating their shared origin. Moreover, molecular karyotype might serve as a strong, inexpensive tool for revealing clonal hematopoiesis in cases of negative targeted next-generation sequencing. Finally, the moderate response of ECD to midostaurin suggests that kinase inhibition might have a potential role in ECD treatment.

Prevalence, distribution and clinical significance of joints, muscles and bones in sarcoidosis: an 18F-FDG-PET/CT study.

OBJECTIVES: In Sarcoidosis joints-muscles-bones (JMBs) localizations are of the least common. 18F-FDG-PET/CT imaging revolutionized detection of JMBs involvement by adding metabolic activity information and allowing for a comprehensive, whole-body mapping of the disease. AIM AND METHODS: This study investigated prevalence, distribution, and clinical significance of JMBs sarcoidosis in 195 consecutive patients that underwent 18F-FDG PET/CT examination. RESULTS: Joint and bone involvement were encountered in 15% of patients with a mean of the maximum-standardized-uptake-value (SUVmax) of 6.1. Most common location was the axial skeleton. Hypercalciuria was significantly more frequent in patients with osseous involvement (p = 0.003). Muscle activity (SUVmax = 2.4) was encountered in 20% of the patients, most frequently in treatment-naïve (p = 0.02). The muscles of the lower extremities were affected the most. Muscle and bone localization coexist in 50% of the cases. JMBs disease was almost asymptomatic, not related to chronicity but to pulmonary, nodal, and systemic disease. Long-term follow-up and treatment response of affected patients confirmed sarcoidosis. CONCLUSION: 18F-FDG-PET/CT revealed JMBs localizations and coexistence with other organ sites supporting the concept that sarcoidosis is a systemic disease. By allowing an integrative interpretation of multi-organ involvement in the context of a pattern highly suggestive of sarcoidosis, it strongly keeps-off the diagnosis of malignancy.

Human white-fat thermogenesis: Experimental and meta-analytic findings.

White adipose tissue (WAT) thermogenic activity may play a role in whole-body energy balance and two of its main regulators are thought to be environmental temperature (Tenv) and exercise. Low Tenv may increase uncoupling protein one (UCP1; the main biomarker of thermogenic activity) in WAT to regulate body temperature. On the other hand, exercise may stimulate UCP1 in WAT, which is thought to alter body weight regulation. However, our understanding of the roles (if any) of Tenv and exercise in WAT thermogenic activity remains incomplete. Our aim was to examine the impacts of low Tenv and exercise on WAT thermogenic activity, which may alter energy homeostasis and body weight regulation. We conducted a series of four experimental studies, supported by two systematic reviews and meta-analyses. We found increased UCP1 mRNA (p = 0.03; but not protein level) in human WAT biopsy samples collected during the cold part of the year, a finding supported by a systematic review and meta-analysis (PROSPERO review protocol: CRD42019120116). Additional clinical trials (NCT04037371; NCT04037410) using Positron Emission Tomography/Computed Tomography (PET/CT) revealed no impact of low Tenv on human WAT thermogenic activity (p > 0.05). Furthermore, we found no effects of exercise on UCP1 mRNA or protein levels (p > 0.05) in WAT biopsy samples from a human randomized controlled trial (Clinical trial: NCT04039685), a finding supported by systematic review and meta-analytic data (PROSPERO review protocol: CRD42019120213). Taken together, the present experimental and meta-analytic findings of UCP1 and SUVmax, demonstrate that cold and exercise may play insignificant roles in human WAT thermogenic activity. Abbreviations: WAT:White adipose tissue; Tenv: Environmental temperature; UCP1: Uncoupling protein one; BAT: Brown adipose tissue; BMI:Body mass index; mRNA: Messenger ribonucleic acid; RCT: Randomized controlled trial; WHR: Waist-to-hip ratio; PRISMA: Preferred Reporting Items for Systematic Reviews and Meta-analyses; PET/CT: Positron Emission Tomography and Computed Tomography; REE: Resting energy expenditure; 18F-FDG: F18 fludeoxyglucose; VO2peak:Peak oxygen consumption; 1RM: One repetition maximum; SUVmax: Maximum standardized uptake value; Std: Standardized mean difference.

Lymphoma Severity and Type Are Associated With Aortic FDG Uptake by 18F-FDG PET/CT Imaging.

BACKGROUND: There is evidence that metabolic disease burden in lymphoma influences patient outcome. However, the impact of disease severity on the cardiovascular system is unknown. OBJECTIVES: The aim of this study was to examine whether lymphoma is associated with arterial inflammation by investigating the relationship between disease metabolic burden and arterial fluorodeoxyglucose (FDG) uptake. METHODS: Sixty-two chemotherapy-naïve patients with active Hodgkin's or non-Hodgkin's lymphoma were matched (2:1) to individual control groups of lymphoma patients previously treated and free of active disease. All groups underwent 18F-FDG position emission tomography-computed tomography imaging. Disease severity was quantified by metabolic tumor volume (MTV) and total lesion glycolysis corresponding to standardized uptake values (SUVs) ≥41% or ≥2.5 of the maximum SUV within lymphoma regions, and aortic FDG uptake was quantified through the target-to-background ratio (TBR). Inflammatory and disease severity biomarkers were also measured. RESULTS: MTV and total lesion glycolysis measurements were significantly correlated with inflammatory and disease biomarkers. Aortic TBR was higher in patients with active non-Hodgkin's lymphoma compared with control subjects (median difference 0.51; 95% confidence interval [CI]: 0.28 to 0.78; p < 0.001). Similarly, patients with active Hodgkin's lymphoma had higher values of aortic TBR compared with control subjects (median difference 0.31; 95% CI: 0.15 to 0.49; p < 0.001). In addition, aortic TBR was modestly increased in patients with stage III to IV disease compared with those with stage I to II disease (median aortic TBR: 2.23 [interquartile range: 2.01 to 2.54] vs. 2.06 [interquartile range: 1.83 to 2.27; p = 0.050). In multivariable analysis, aortic FDG uptake and MTV≥2.5 values were independently associated (ß = 0.425; 95% CI: 0.189 to 0.662; p = 0.001; R2 = 0.208), as were aortic FDG uptake and MTV≥41% (ß = 0.407; 95% CI: 0.167 to 0.649, p = 0.001; R2 = 0.191). CONCLUSIONS: Aortic wall FDG uptake is related with disease severity indicative of a possible vascular effect of lymphoma. This work highlights a new potential role of molecular imaging in cardio-oncology for evaluating disease severity and its consequences on the vasculature.

Adjustment of vascular 2-deoxy-2-[18F]fluoro-D-glucose uptake values over time through a modeling approach.

To develop and test a model predicting 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) standardized uptake value (SUV) changes over time in the aorta and the superior vena cava (SVC). Maximum aortic SUV and mean SVC SUV were determined at two time points (T1 and T2) in the ascending (ASC), descending (DSC), abdominal (ABD) aorta, aortic arch (ARC) and SVC of patients who have undergone [18F]FDG PET/CT for clinical purposes. For SUV prediction at T2, linear and non-linear models of SUV difference for a given time change were developed in a derivation group. The results were tested in an independent validation group, whilst model reproducibility was tested in patients of the validation group who have undergone a second clinically indicated scan. Applying the linear model in the derivation group, there were no statistically significant differences in measurements obtained in the examined segments: mean differences ranged from 0 ± 0.10 in SVC to 0.01 ± 0.13 in ARC between measured and predicted SUV. In contrast, in the non-linear model, there were statistically significant differences in measurements, except in ARC, with mean differences ranging from 0.04 ± 0.14 in ARC to 0.28 ± 0.13 in ABD. In the validation group using the linear model, there were no statistically significant differences, with mean differences ranging from - 0.01 ± 0.08 in ASC to - 0.03 ± 0.11 in ABD. Regarding reproducibility, mean differences were no statistically significant, ranging from 0.004 ± 0.06 in ASC to - 0.02 ± 0.16 in ABD. We have developed a linear model allowing accurate and reproducible prediction of SUV changes over time in the aorta and SVC.

Vascular inflammation and metabolic activity in hematopoietic organs and liver in familial combined hyperlipidemia and heterozygous familial hypercholesterolemia.

BACKGROUND: Familial dyslipidemias of either heterozygous (heFH) or combined (FCH) type lead to accelerated atherogenesis and increased cardiovascular risk. OBJECTIVE: The aim of this study was to investigate in statin-naïve adult patients with familial dyslipidemias whether inflammatory activation and liver, spleen and bone marrow metabolic activity differ compared with normolipidemic subjects and between dyslipidemic groups. METHODS: Fourteen patients with FCH, 14 with heFH, and 14 normolipidemic individuals were enrolled. Serum lipids, high-sensitivity C-reactive protein, and fibrinogen levels were measured, followed by 18F-fluorodeoxyglucose positron-emission tomography/computed tomography imaging. Radiotracer uptake in the aortic wall, spleen, bone marrow, and liver was quantified as tissue-to-background ratio (TBR). RESULTS: Patients with heFH had significantly higher low-density lipoprotein levels compared with those with FCH and controls (P < .001). However, aortic TBRs were higher in FCH compared with heFH patients and controls (P = .02 and P < .001, respectively). FCH patients exhibited higher FDG uptake in the spleen compared with controls (P = .05). In addition, FCH exhibited higher bone marrow FDG uptake compared with heFH patients and controls (P = .03 and P = .02, respectively). FCH had higher liver uptake compared with heFH patients and controls (P < .001 for both). Significant correlations were observed between inflammatory biomarkers and imaging indices as well as between aortic TBR and FDG uptake of hematopoietic organs and liver. CONCLUSIONS: Systemic, as well as vascular inflammation and spleen, bone marrow, and hepatic metabolic activity are increased in patients with FCH despite lower levels of low-density lipoprotein.

Inhibition of Aortic Valve Calcification by Local Delivery of Zoledronic Acid-an Experimental Study.

The aim of this study was to evaluate in an experimental model of aortic valve (AV) stenosis the effectiveness of zoledronate on the inhibition of calcification. Sixteen New Zealand rabbits were placed on vitamin D-enriched diet for 3 weeks. All animals underwent PET/CT at baseline and before euthanasia to assess calcification. Thereafter, the AVs of eight animals were treated with local delivery of 500 µg/l zoledronate. A placebo mixture was administered in the remaining eight animals. Standardized uptake values were corrected for blood pool activity, providing mean tissue to background ratios (TBRmean). In the zoledronate group, there was no progression of AV calcification (TBRmean 1.20 ± 0.12 vs 1.17 ± 0.78,p = 0.29), while AV calcification progressed in the placebo group (1.22 ± 0.15 vs 1.53 ± 0.23,p = 0.006). Ascending aorta (AA) calcification progressed in both zoledronate and placebo groups. Histology confirmed the results of the PET/CT. Inhibition of AV calcification by local delivery of zoledronate is feasible and effective.

Inflamed human carotid plaques evaluated by PET/CT exhibit increased temperature: insights from an in vivo study.

AIMS: To explore the relationship between temperature measurements derived by microwave radiometry (MWR) and carotid flurodeoxyglucose (FDG) uptake and assess their association with histological and immunohistochemistry findings in patients with high-grade carotid stenosis. METHODS AND RESULTS: In 21 patients undergoing carotid endarterectomy, carotid inflammation was evaluated by both FDG positron emission/computed tomography (FDG-PET/CT) imaging and MWR measurements. Carotid inflammation was assessed by PET/CT as target-to-background ratio (TBR) by obtaining measurements in consecutive axial slices 2 cm below to 2 cm above the carotid bifurcation. Temperature difference (ΔT) by MWR was assigned as the maximum-minimum temperature measurements over the corresponding carotid segments. The extent of lipid core, calcification as well as CD68 and CD31 levels were also assessed. There was a significant correlation between ΔT values and FDG uptake (R = 0.40, P = 0.01), but no correlation between the degree of angiographic stenosis and ΔT values (R = -0.02, P = 0.91) or PET/CT measurements (R = -0.28, P = 0.86). Patients with plaques containing high lipid core extension or low calcification exhibited higher ΔT (P = 0.001 and P < 0.001, respectively) and FDG uptake values (P = 0.02 and P = 0.02, respectively). Patients with plaques containing increased CD68 expression exhibited higher ΔT and FDG uptake measurements. CONCLUSION: Carotid plaque inflammation was evaluated by temperature measurements, which were correlated with FDG-PET/CT indices, confirmed by histopathology and immunohistochemistry findings. Structural changes did not predict inflammatory process. The implications of these findings in risk stratification and management of patients with carotid atherosclerosis and the precise algorithm for potential clinical utilization of MWR and PET/CT remain to be determined.

Positron emission tomography in spinal infections.

Magnetic resonance imaging is the imaging method of choice for diagnosing infection of the spine in unoperated cases. 2-[(18)F]-fluoro-2deoxy-d-glucose positron emission tomography/computed tomography study is recommended to distinguish between spinal infection and common Modic change in patients with metallic implants and prosthetic replacements and for differentiating tuberculous from pyogenic spondylitis in ambiguous cases, reflecting the activity of the infection. Also, it seems to have a strong clinical impact in more than half of patients with infectious spondylitis, while it is superior to other imaging techniques in revealing residual disease after treatment and early response to therapy. New tracers as well as new hybrid modalities are under investigation.

(18)F-fluorodeoxyglucose positron emission tomography/computed tomography in infected polycystic kidney disease.

A positron emission tomography/computed tomography (PET/CT) study using (18)F-fluorodeoxyglucose ((18)F-FDG) was performed in a 54-year-old female with polycystic kidney disease, fever, and abdominal discomfort. Cyst's infection was suspected, but CT and U/S findings were not specific to accurately depict pyocysts and guide surgical treatment. In PET/CT, both kidneys are enlarged with multiple cysts and little remaining parenchyma. There is intense focal or ring-shaped FDG uptake in cysts in the upper and lower poles of the left kidney indicative of active infection. There is also increased FDG uptake in para-aortic lymph nodes bilaterally. Hepatic and right renal cysts do not present increased FDG uptake. As this case illustrates, FDG PET/CT can be helpful for the precise localization of cyst infections in patients with polycystic kidney disease considered for surgical treatment.